How Deep clone works

DineshOjha
New Contributor III

Hi,

For DR purposes, we have setup Deep clone using delta share. Each time the deep clone job runs, it executes the query 

create or replace table {schema}.{table} deep clone {delta_share}.{schema}.{table} 
The 1st time the job ran, it took few hours to complete, but it has been completing in 15 mins for the subsequent runs.
From my understanding, deep clone replaces the entire table each time, so why did the job take few hours to deep clone for the 1st run and lesser time after that?
Can someone please help understand how deep clone works with delta share?